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Power Platform Community / Forums / Power Automate / Invalid append to string
Power Automate
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Invalid append to string

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Posted on by 49

Hi Team, 

 

I'm getting the error below, but no idea how to solve it.

Error detail as below : 

Unable to process template language expressions in action 'Append_to_string_variable' inputs at line '0' and column '0': 'The template language function 'formatDateTime' expects its first parameter to be of type string. The provided value is of type 'Null'. Please see https://aka.ms/logicexpressions#formatdatetime for usage details.'.

Marthini_06_0-1691718707661.png

 

Marthini_06_1-1691718761455.png

 

Marthini_06_2-1691718780975.png

 

 

 

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  • Verified answer
    trice602 Profile Picture
    16,135 Super User 2026 Season 1 on at

    Hi @Marthini_06 ,

     

    Yeah so your formatDateTime() expression is a date type and you need to convert to a string.  Please wrap your existing formatDateTime expression in a string() such as string(formatDateTime(your_code)).  This will convert that value to a string and you can keep going.  Please mark as a solution if this help!  Always glad to help! Tom

  • Marthini_06 Profile Picture
    49 on at

    Hi @trice602 ,

     

    Thank you so much. It works as expected !

  • trice602 Profile Picture
    16,135 Super User 2026 Season 1 on at

    Nice!  There is never a better feeling than getting a flow to run successfully! Always glad to help! Tom

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